The British patent application 1 526 703 describes a press control for a radial feed pellet mill, in which the speed of the extruding die is controlled as a function of the counter-torque in such a way that the installation is utilized in the best possible way.
In this installation, the control works as follows:
With the die driven, the rotating speed is regulated by a torque converter in such a way that, with respect to the most economic operating mode, it is optimally adapted to the counter-torque with the throughput taken into account. With a constant supply of raw material and with a high counter-torque, the speed, by way of example, is being kept constant until the counter-torque exceeds the maximum driving moment. Thereupon, the driving speed naturally decreases with the counter-torque keeping on increasing, and only on falling below a certain minimum speed is the supply of raw material reduced.
This control cannot intervene to prevent slippage, since the rotating speed of the rolls is not taken into account and is not compared with the speed of the die to detect slippage.
The DE-OS 38 06 945 reveals an edge-runner mill in which the die and the pan rolls or the motion of rotation of the pan head and the revolution of the pan rolls are driven independently of each other, so that a preselected relative speed between the die and the surface of the pan rolls is reached at a point located nearest to the die.
Such a mill has no control of slippage, but a pre-selectable slip setting.